The currents or electromotive forces which are included in the sheaths and screens of the three single core cables making up a three-phase cable installation can be untolerably high, but they can be eliminated by dividing the screens into isolated sections and crossbonding them. So far, the screen interruptions have always been made at the same site as the cable joints. The screens are crossbonded at the interruption sites and the screens are usually grounded for every third cable section.
In Cigre report No. 21-08 of 1986 there is described design, manufacturing and installation of XLPE cables in Denmark. ("XLPE" stands for "crosslinked polyethylene".) In connection with sectionalizing joints, there are described three different principles for interruption of the screens in such cables. Of the three different systems, 1 (a double stress cone system), 2 (a screen overlap system), and 3 (a high resistivity system), the first one is in our opinion the best alternative. As mentioned in said article, special care must be taken to ensure that the metallic connections from the stress cone to the metal sheath of the cable and to the bonding leads do not mechanically influence the position of the stress cone. It is also mentioned that allowance has to be made for the methane gas from the vulcanized joint insulation to escape without forming air pockets in the interface between the XLPE insulation and the stress cone.